The invention relates generally to a method of reducing the microbial load on foods. More specifically, this invention relates to a method of disinfecting, sanitizing, or sterilizing foods involving the use of ozone in combination with a surfactant.
Ozone is an unstable triatomic allotrope of oxygen. It is produced in an energized environment wherein molecular oxygen dissociates into monatomic oxygen which subsequently collides and recombines with an oxygen molecule to form a highly reactive ozone molecule.
Although ozone is primarily employed in disinfection, it can perform other functions such as color reduction, odor and taste removal, algae control, oxidation of inorganic and organic compounds in water and waste-water treatment practices, waste gas treatment and bleaching of paper pulp.
The most prominent features of ozone as a biocide lie in its speed and selectivity in oxidation. Biocidal effects are believed to primarily be achieved through oxidation. Consistent with this belief, the ability of any chemical to reduce microbial viability is in direct proportion to its oxidation potential. Ozone is the fourth most powerful oxidizing agent known; only fluorine, fluorine dioxide, and monatomic oxygen are thought to be more reactive. Ozone possesses an oxidation potential of 2.07 millivolts relative to chlorine gas"" 1.36 millivolts. It is important to note that an increased oxidation potential is indicative of an accelerated bacterial kill. The rate of disinfection has been demonstrated to be more than 3,000 times faster than chlorine; thus contact time is a lesser consideration in the application of ozone as a microbicide.
Disinfection with the use of ozone may proceed by oxidation directly and by intermediate hydroperoxy compounds that can interact with cytosolic components. Organic ozone chemistry would predict that oxidized organic compounds containing carbon-carbon double bonds give rise to hydroperoxyalcohols. Evidence exists that organic peroxides exert a stronger bacteriocidal action than hydrogen peroxide due to a greater tendency to decompose. No evidence is believed to exist in the literature of any microorganism that is resistant to the effects of ozone exposure. The application of ozone is preferable due to its compatibility with biota. There are no residual or harmful reaction products downstream particularly in the range of 0-20 ppm. The presence of peroxidic compounds could be perceived to be harmful to the biota, but toxicity studies indicate the contrary to be true. Studies have shown that these compounds are chemically highly unstable and rapidly decompose. It has also been shown that these compounds can be removed by other oxidizing molecules.
In addition to demonstrating powerful capabilities in the destruction or inactivation of bacteria, fungi and protozoa; ozone has been shown to be virucidal. The efficacy of ozone has been reported to range from (all of the following values given reported a 99% reduction) 2.2 mg/l for Escherichia coli in 19 minutes from raw waste water; 0.02 mg/l for Candida tropicalis in 0.30 minutes from ozone-demand free water; 1.2 mg/l for Naegleria gruberi in 1.1 minutes from ozone-demand free phosphate buffer solution and 0.2 mg/l for Poliovirus type I in 9 minutes from activated sludge effluent. With regard to bacterial spores (specifically, Bacillus subtilis v. globigii), ozone has been shown to achieve a four-log reduction within 1.5-2 minutes when water is purged with 3% ozone by weight. Using a non-toxic concentration of 4 xcexcg ozone per ml of serum, ozone can achieve a six-log reduction in the infectious titer of human immunodeficiency virus (xe2x80x9cHIVxe2x80x9d).
Presently, two methods of xe2x80x9cbioburdenxe2x80x9d reduction are used on food: high temperature pasteurization, and chemical disinfection. The high temperatures used in pasteurization denature proteins and degrade the organoliptics present in food, altering both texture and flavor. Surfactant use alone is incapable of disinfecting to the degree of high temperature pasteurization. Chemical disinfection can leave behind undesirable residues.
Currently, commercial preparation of many foods, which do not normally require cooking, requires the use of high temperature heat pasteurization to disinfect ingredients before they are used. This results in foods that do not have acceptable flavor and texture. A need exists for a reliable cold water method of reducing food bioburden to acceptable levels.
It would be an improvement in the art to have a relatively economical, reliable method of disinfecting, sanitizing or sterilizing foods, which is similar in effectiveness to high temperature pasteurization, yet uses low temperatures to preserve flavor and texture.
The invention includes a method of reducing microbial load on food, the method comprising: applying an ozonated wash liquor to the food, applying a surfactant to the food, and maintaining the application of ozonated wash liquor and surfactant to the food for a sufficient amount of time to reduce the microbial load on the food. In the method, the application of the ozonated wash liquor to the food can occur before, during, and/or after the application of surfactant to the food. The application of ozonated wash liquor and surfactant to the food should preferably occur for a sufficient amount of time to remove soils and chemical contaminants from the food (such as fertilizers, pesticides, herbicides, mycotoxins, and mixtures of any thereof).
The invention also includes a method of reducing the microbial load on foods through the use of a spray with or without scrubbing and/or a bath with or without agitation. The method includes introducing the food and a surfactant containing wash liquor into the bath, thus bringing the food and wash liquor into contact to wet the surface of the food. Generally, the surfactant containing wash liquor will contact the food for a period of time ranging from about 1 minute to about sixty (60) minutes. A combination of ozone gas, oxygen and/or air is mixed into the wash liquor to form an ozonated wash liquor. Preferably, this ozonated wash liquor contacts the food for a period of time ranging from about one (1) minute to sixty (60) minutes.
In one embodiment, the method is used for the disinfection of xe2x80x9cshiny-skinnedxe2x80x9d fruits, such as apples, pears, peaches and the like. This method comprises contacting the whole fruit with a wash liquor at a temperature of about 0xc2x0 C. (Celsius) to about 50xc2x0 C. The wash liquor is an admixture of aqueous solution and a oleic, or citirc acid containing surfactant. The fruit is thus wetted. A gaseous mixture of ozone gas, oxygen and/or air is mixed with the wash liquor to form an ozonated wash liquor containing from about 0.01 ppm to about 15 ppm ozone. The ozonated wash liquor is then allowed to contact the fruit for a period of time ranging from about one (1) minute to about sixty (60) minutes (preferably five to fifteen minutes) thus disinfecting the surface of the fruit.
The process results in disinfected, sanitized, or sterilized fruit. As shown herein bacterial spores are even killed. The temperature can be greatly reduced relative to using high temperature pasteurization, while retaining similar disinfecting capabilities. Alkalinity can also be reduced relative to using only surfactant as a disinfectant. This allows for the preservation of the texture and flavor of the fruit, by avoiding protein denaturation and organoliptic degradation. The application of the ozone and surfactant combination in disinfection, sanitization or sterilization processes results in improved texture and flavor quality.